“Energy” has become one of the important issues to be developed and resolved, recently. Thus, many countries have started to develop and invest in renewable energy sources. Solar energy is an unlimited and non-polluting energy source; furthermore, the development and application of the solar energy are not limited by the topography, geomorphology or other relating factors; therefore solar energy becomes one of the most important renewable energies. Solar energy can be directly converted to commonly used electricity by an appropriate equipment or device. An equipment or device converting the solar energy to electricity is called a solar cell.
Recently, a new type of the solar cells known as dye-sensitized solar cells (DSCs), has been proposed by the Switzerland professor, Micheal Grätzel. Dye-sensitized solar cells have many advantages, such as a low manufacturing cost, good photoelectric conversion efficiency, high transparency, colorfulness, flexibility, and etc.; therefore dye-sensitized solar cells have been concerned in the industry application. Generally, a dye-sensitized solar cell is constituted with four major components: an anode/cathode for providing a channel of the current flow, a semiconducting material such as TiO2 or ZnO for accepting and transporting electrons, a dye layer adsorbed on the surface of the semiconducting material via self-assembly, and an electrolyte for transforming electronic holes. The materials and the interfaces between each component of the dye-sensitized solar cells play important roles on the conversion efficiency of the device. Most particularly, photosensitizer dyes are critical in determining the efficiency of the dye-sensitized solar cells. Thus, searching for the high efficiency photosensitizer dyes has become one of the most active research activities in the past two decades.